Array assays between surface bound binding agents or probes and target molecules in solution may be used to detect the presence of particular biopolymers. The surface-bound probes may be oligonucleotides, peptides, polypeptides, proteins, antibodies or other molecules capable of binding with target molecules in solution. Such binding interactions are the basis for many of the methods and devices used in a variety of different fields, e.g., genomics (in sequencing by hybridization, SNP detection, differential gene expression analysis, identification of novel genes, gene mapping, finger printing, etc.) and proteomics.
One typical array assay method involves biopolymeric probes immobilized in an array on a substrate such as a glass substrate or the like. A solution containing analytes that bind with the attached probes is placed in contact with the substrate, covered with another substrate to form an assay area and placed in an environmentally controlled chamber such as an incubator or the like. Usually, the targets in the solution bind to the complementary probes on the substrate to form a binding complex. The pattern of binding by target molecules to biopolymer probe features or spots on the substrate produces a pattern on the surface of the substrate and provides desired information about the sample. In most instances, the target molecules are labeled with a detectable tag such as a fluorescent tag, chemiluminescent tag or radioactive tag. The resultant binding interaction or complexes of binding pairs are then detected and read or interrogated, for example by optical means, although other methods may also be used. For example, laser light may be used to excite fluorescent tags, generating a signal only in those spots on the biochip that have a target molecule and thus a fluorescent tag bound to a probe molecule. This pattern may then be digitally scanned for computer analysis.
As will be apparent, control of the assay environment and conditions contributes to increased reliability and reproducibility of the array assays. However, merely placing a slide over the substrate or positioning a cover slip over the substrate, as is commonly done, is often insufficient to allow precise control over the assay and is labor intensive as well.
During an array assay such as a hybridization assay, the assay is often performed at elevated temperatures and care must be taken so that the array does not dry out. Using a second slide positioned over the substrate allows contents to leak and/or evaporate which can result in the array drying out during use, adversely impacting the assay. In addition, the substrate cannot be tipped or moved from the horizontal position without risk that the substrate or cover slip will slip off. Maintaining the array in a humid environment may reduce drying-out, but offers only an incomplete solution.
Various chambers or containers have been developed to eliminate the use of a substrate or cover slip and facilitate the above described array assays. However, while many of these chambers are effective, they often require the user to manually assemble the apparatus around an array using screws to maintain the structure together. Such procedures take time and may introduce contaminants into the array due to the increased handling thereof during assembly of the apparatus.
Thus, there continues to be an interest in the development of new devices for array-based hybridizations and methods of using the same. Of particular interest is the development of an array assay device, and methods of use thereof, that is easy to assemble and use, includes minimal components, prevents drying out of the array and that may also be capable of testing multiple samples with multiple arrays without cross contamination.